1. Field of the Invention
The invention relates to a burner for operating a heat generator.
2. Brief Description of the Related Art
EP-0 780 629 A2 describes a burner on the incoming flow side of a rotation generator, in which the generated rotational flow is transferred seamlessly into a mixing section. This is accomplished using a flow geometry formed at the start of the mixing section for this purpose, the flow geometry including transition channels that, according to the number of tangentially acting flow-in channels or flow-in slits of the rotation generator, sectorially form the front face of the mixing section and extend rotationally in the flow direction. On the outgoing flow side from these transition channels, the remaining mixing section has a number of film formation bores through which a volume of air flows into the mixing section and which induces an increase in the flow speed along the pipe wall. This is followed by a combustor, the transition between the mixing section and the combustor being formed by a change in the cross-section, in the plane of which a flow-back zone or flow-back bubble is formed.
The intensity of the rotation in the rotation generator accordingly is chosen in such a way that the vortex does not burst inside the mixing section but further downstream as explained above, in the area of the change in the cross-section. The length of the mixing section is such that it ensures an adequate premixing quality for all types of fuels used.
Although this burner represents a leap in quality when compared with those of the previous state of the art in regard to strengthening flame stability, lower pollutant emissions, reduced pulsations, complete burnout, large operating range, good cross-ignition between the various burners, compact design, improved mixing, etc., it was found that instabilities may develop in the transient ranges and with partial loads. This is in particular related to the fact that when this burner functions together with a pilot burner system, this burner is operated in the range of about a 50% partial load near the lean extinguishing limit. In the process, the flame becomes more unstable, and extinguishing pulsations may occur, i.e., extinguishing the flame is caused by combustor oscillations. While a stabilization may be achieved with a small amount of pilot gas, this drastically increases pollutant emissions.